Study Gives Odds On Aids Contraction

April 22, 1988|The New York Times

WASHINGTON -- The chance of catching the AIDS virus from a single act of heterosexual intercourse with a low-risk partner is 1 in 5 billion if a condom is used and the partner has been tested and found free of the virus, according to a report published in the current issue of The Journal of the American Medical Association.

The risk for that one sexual encounter rises to 1 in 500 if the partner is known to be infected and no condom is used.

The report by two San Francisco researchers is the first published effort in an authoritative journal to calculate the odds of contracting an AIDS infection from heterosexual intercourse with individuals from various backgrounds.

Its central finding is that the degree of risk is overwhelmingly determined by whether one`s sexual partner is from one of the groups that is at high risk of contracting AIDS -- bisexual men, intravenous drug users or prostitutes.

The report`s ``single most important recommendation`` is that heterosexuals should protect themselves from AIDS by having sexual relations only with partners they know are at low risk of infection.

Careful choice of partners provides far greater protection against AIDS than using a condom, avoiding anal intercourse, reducing the number of sex partners, or simply requiring that one`s partner pass an AIDS test demonstrating lack of infection, the report concludes.

The new analysis, published in the April 22 issue of the medical journal, was prepared by Dr. Norman Hearst and Dr. Stephen B. Hulley, epidemiologists at the medical school of the University of California at San Francisco.

Other experts warned that, while the estimates are generally sound, they are group averages that do not reflect the wide variation among individuals in their chances of being infected with the AIDS virus or their ability to transmit it to a sex partner. Some individuals might face far more danger of contracting AIDS from a heterosexual encounter than the estimates suggest; others might face far less danger.